A HISTORY OF DERBYSHIRE 



surmounted with piles of rock weathered into fantastic shapes. Robin 

 Hood's Stride and the Rowtor Rocks near Rowsley exhibit the 

 characteristic weathering of this grit. The Black Rocks near Cromford, 

 so named from their black surface, probably due to the action of 

 vegetation, form part of an escarpment of the Kinder Scout Grit. 



The third, or Chatsworth or Rivelin Grit, varies greatly in charac- 

 ter. It is a coarse conglomerate in the centre of the district, and further 

 south becomes a fine grained sandstone. It is sometimes called the 

 Escarpment Grit, because its outcrop forms escarpments which often 

 extend for miles along the county, and make a distinctive feature in the 

 scenery. Amongst these edges or escarpments are Crow Chine and 

 Stanage Edges. 



The rocks between the third and first grits are made up of shales 

 and sandstones which vary in thickness and horizontal extent, beds of 

 gannister and thin coals. The first or topmost grit, known as the Rough 

 Rock, is the most constant of the Millstone Grit group, both in thick- 

 ness and in character. Its average thickness is 100 feet. It is a massive 

 coarse grit with a large proportion of felspar, the decomposition of which 

 renders the rock loose and crumbly. The same bed of grit often varies 

 greatly in character from a coarse conglomerate to a fine grained sand- 

 stone, and no particular grit in the series can be identified by its litho- 

 logical appearance. The sequence can only be found by tracing the 

 successive beds along the country. Traces of coal are found on the top 

 of each of the five grits of this series. 



COAL MEASURES 



The Derbyshire coalfield forms part of the largest coalfield in 

 England, viz. that which occupies portions of the counties of Derby, 

 Nottingham and York. It is bounded on the east by an escarpment of 

 magnesian limestone, which lies above the Coal Measures and extends 

 from near Nottingham in a northerly direction, far beyond the limits 

 of the great coalfield. On the west it is underlain by the Millstone Grit, 

 Yoredales and Mountain Limestone, which with their easterly dip rise 

 into the ridge of the Pennine Chain. On the western side of the 

 Pennine Chain are the south Staffordshire and north Staffordshire and 

 Cheshire coalfields. A comparison of the carboniferous rocks on the 

 east and west side of the Pennine anticline has shown that though there 

 is on the east a general diminution in the thickness of the strata, they 

 can be correlated from the Millstone Grit up to the lower beds of the 

 middle Coal Measures. This correlation of the beds on opposite sides of 

 the anticline, taken in connection with the fact that there lies between 

 them an elongated dome of Mountain Limestone, is sufficient to lead to 

 the conclusion that originally the Coal Measures extended over part of 

 the north of England almost from the coasts of Lancashire and Cheshire 

 into Nottinghamshire, and perhaps as far east as the river Trent. The 

 denudation which has taken place since the Pennine upheaval has 



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